Hello @Dyce welcome to the community. Super happy that you’re enjoying our work!
Just chatting with a colleague, we think that this is a feature we don’t currently support. That being the case it would be GREAT if you would be able to raise a GitHub issue? We have some notes to help you along here.
You could try deleting from the materialized view that’s “underneath” the continuous aggregate (it may work). We also think it’s possible that an upcoming version might support it, but raising the GH issue may well get you the answer on that.
It would be useful to understand the use case. Is it just that you don’t want the old data hanging around or is it essential for it to be “gone”? That’s just for interest, but it also helps support a feature request too.